Method for producing zinc etheromycin from fermentation broths

ABSTRACT

Zinc complexes of glycolic monovalent monoglycoside polyether antibiotics are provided for use as coccidiostats and growth-promoting agents when administered to poultry and for use as active agents for improving cardiovascular function in animals. 
     Zinc complexes of the type disclosed can be prepared by adding soluble zinc salt to a fermentation beer containing the glycolic monovalent monoglycoside polyether antibiotic to thereby form an insoluble, recoverable biomass containing the desired zinc antibiotic complex.

The present invention relates to methods for producing zinc complexes of glycolic monovalent monoglycoside polyether antibiotics. The present invention further relates to processes for the administration of zinc complexes of glycolic monovalent monoglycoside polyether antibiotics to poultry to promote poultry growth, to enhance poultry feeding efficiency, and/or to combat coccidial infections in poultry. In addition, the present invention relates to feed compositions and feed additive compositions containing zinc complexes of glycolic monovalent monoglycoside polyether antibiotics. The present invention also relates to processes for improving cardiovascular function in animals by administering zinc complexes of glycolic monovalent monoglycoside polyether antibiotics. The present invention further relates to pharmaceutical compositions including zinc complexes of glycolic monovalent monoglycoside polyether antibiotics for improving cardiovascular function in animals. The present invention also relates to methods for the purification of zinc complexes of glycolic monovalent monoglycoside polyether antibiotics which are formed in fermentation beer such that the zinc complexes are more suitable for administration to an animal such as a human being.

The group of compounds known as polyether antibiotics can be generally characterized as carboxylic acid ionophores which can be produced by culturing Streptomyces type microorganisms. The polyether antibiotics have a basic structure generally consisting essentially of the elements oxygen, hydrogen and carbon and possibly nitrogen and have a molecular weight in the range of about 300 to about 1800, most often from about 400 to about 1200. They have low solubility in water, are generally soluble in low molecular weight alcohols, ethers and ketones, and have at least one, and usually one or two, carboxylic acid groups. A generally comprehensive review of this class of antibiotics is set forth in Westley, Adv. Appl. Microbiology 22, 177-223 (1977). As is mentioned therein, at least twenty different polyether antibiotics were known at the time the article was written. Since then, additional polyether antibiotics have been discovered.

In the previously noted publication, Westley classified the known polyether antibiotics into four separate classes based on ability of the particular antibiotic to effect the transport of divalent cations and based on the chemical structure of the particular antibiotic. Using these criteria, Westley defined class 1a as those polyether antibiotics which are monovalent polyethers antibiotics. In addition, the polyether antibiotics of this class have a generally linear configuration, i.e., the carboxylic portion of the polyether molecule is attached either directly or indirectly to a terminal ring structure. They generally include from about four to about six tetrahydropyran and/or -furan structures and up to six total ring structures. Included in class 1a are the polyether antibiotics monensin, laidlomycin, nigericin, grisorixin, salinomycin, narasin, lonomycin, X-206, SY-1, noboritomycins A and B, mutalomycin, and alborixin. For clarity, the polyether antibiotics of this class can be referred to as "linear monovalent polyether antibiotics."

Class 1b of the polyether antibiotics was defined by Westley as monovalent monoglycoside polyether antibiotics. These polyether antibiotics, as the class name suggests, include a glycoside type structure, more specifically, a 2,3,6-trideoxy-4-O-methyl-D-erythrohexapyranose moiety, which is attached to the polyether molecule such that a non-linear type molecule is formed, i.e., the carboxylic portion of the polyether molecule is attached either directly or indirectly to a non-terminal ring structure or the molecule has a side chain ring structure, e.g., a 2,3,6-trideoxy-4-O-methyl-D-erythrohexapyranose moiety. Generally, the polyether antibiotics of this class contain about six or seven tetrahydropyran and/or -furan structures.

Class 1b can be further subdivided based on the criteria of chemical structure, among others, into a subclass of non-glycolic monovalent monoglycoside polyether antibiotics and into a subclass of glycolic monovalent monoglycoside polyether antibiotics. The polyether antibiotics of the former subclass may be characterized by the fact that the glycoside group is attached onto a furan or pyran ring type structure which contains fewer than two hydroxyl groups, i.e., 0 or 1 hydroxyl groups. The polyether antibiotics of the latter subclass may be characterized by the fact that the glycoside group is attached onto a furan or pyran type structure which contains two adjacent hydroxyl groups, i.e. a glycolic type structure. Included in the subclass of non-glycolic monovalent monoglycoside polyether antibiotics are the antibiotics septamycin, dianemycin, A-204, lenoremycin and carriomycin. The subclass of glycolic monovalent monoglycoside polyether antibiotics includes etheromycin.

Class 2a as defined by Westley is directed to divalent polyether antibiotics. These antibiotics are generally of a generally linear configuration, may contain from about two to about three tetrahydropyran and/or -furan structures, up to three total ring structures and no nitrogen atoms. Included within class 2a are the antibiotics lasalocid and lysocellin. For clarity, the polyether antibiotics of this class can be referred to as "non-nitrogen containing divalent polyether antibiotics." Class 2b of the polyether antibiotics is directed to divalent pyrrole ethers and thus, in contrast to the antibiotics of the other classes, the class 2b antibiotics contain one or more nitrogen atoms. Included in this class are the antibiotics X-14547 and A-23187.

Glycolic monovalent monoglycoside polyether antibiotics have generally heretofore been recovered in the form of their sodium and/or potassium salts by use of multi-step extraction operations employing organic solvents. As an example, a preferred method of separation and recovery for the glycoclic polyether antibiotic etheromycin is set forth in U.S. Pat. No. 4,129,578 to Celmer et al. In the disclosed method, the whole (unfiltered) fermentation broth containing the antibiotic is twice extracted with about 1/5 to 1/2 volume of methyl isobutyl ketone. The solvent extract is concentrated under vacuum to an oily residue which is then slurried in chloroform:hexane (1:1) and added to a silica gel column. The silica gel column is successively developed with hexane, chloroform:hexane (1:1) and chloroform. The main antibiotic fraction is eluted with ethyl acetate. The eluate is concentrated under vacuum, taken up in acetone and stirred for about 30-60 minutes with activated charcoal. The charcoal is removed by filtration, the solution concentrated to a small volume under vacuum, a small amount of water added and the pH adjusted with sodium hydroxide to 8.0-8.5. The crystalline material that separates is removed by filtration, washed with water and dried. The antibiotic that is isolated at this stage is a mixed sodium and potassium salt of etheromycin formed with both sodium and potassium ions occurring in and scavenged from the fermentation broth and the added sodium hydroxide.

As is apparent from the above recitation of one example of a known recovery process for a glycolic monovalent monoglycoside polyether antibiotic, such processes can be quite complicated and can require the use of relatively large quantities of various organic solvents, at least some of which may be quite expensive. In addition, such solvent recovery processes inevitably will suffer antibiotic yield losses as well as losses of the various organic solvents used in the process. There is thus a continuing need for antibiotic preparation and recovery processes which effectively and efficiently produce polyether antibiotics in a form suitable for use as feed additives.

In one aspect, the present invention relates to methods for producing zinc complexes of glycolic monovalent monoglycoside polyether antibiotics. In another aspect, the present invention relates to processes for the administration of zinc complexes of glycolic monovalent monoglycoside polyether antibiotics to poultry to promote poultry growth, to enhance poultry feeding efficiency, and/or to combat coccidial infections in poultry. In yet a further aspect, the present invention relates to feed compositions and feed additive compositions containing zinc complexes of glycolic monovalent monoglycoside polyether antibiotics. In yet another aspect, the present invention relates to processes for stimulating cardiovascular function in animals by administering zinc complexes of glycolic monovalent monoglycoside polyether antibiotics. In a further aspect, the present invention relates to pharmaceutical compositions including zinc complexes of glycolic monovalent monoglycoside polyether antibiotics adapted for use in improving cardiovascular function in animals, particularly in mammals. In still another aspect, the present invention relates to methods for the purification of the zinc complexes of a glycolic monovalent monoglycoside polyether antibiotics which are formed in fermentation beers so that the zinc complexes are suitable for administration to a patient requiring improvement in cardiovascular function, e.g., myocardial stimulation. Glycolic monovalent monoglycoside antibiotics useful in the methods and processes of the present invention include the preferred antibiotic etheromycin.

For convenience, the term "glycolic polyether antibiotic" is used hereinafter for the term "glycolic monovalent monoglycoside polyether antibiotic." In addition, the terms "zinc complex" or "complex" are used hereinafter as meaning "a zinc complex of a glycolic polyether antibiotic."

In accordance with the present invention, zinc complexes of glycolic polyether antibiotics can be advantageously formed by adding water-soluble zinc salts to the fermentation broth in which such antibiotics have been produced. When formed in a fermentation beer, the formation of these complexes facilitates the recovery of the glycolic polyether antibiotics from the fermentation beer in which the antibiotics can be produced by, among other things, avoiding the necessity of using recovery methods which involve extractions with the organic solvents followed by their subsequent purification and reuse. The resulting broth-insoluble zinc complexes of the glycolic polyether antibiotics can then be recovered from the broth and employed, for instance, as coccidiostatic, feeding efficiency improving and growth-promoting agents for poultry. Upon further purification of the recovered zinc complexes by suitable methods the zinc complexes may be utilized in stimulating cardiovascular function in animals.

A fermentation broth containing a glycolic polyether antibiotic can be prepared in conventional manner by fermenting a nutrient-containing liquid fermentation medium inoculated with a Streptomyces microorganism capable of producing the desired antibiotic. Suitable liquid fermentation media are generally aqueous dispersions containing a source of assimilable nitrogen and carbohydrates. Nitrogen sources for use in the fermentation media herein can include, for example, yeast, yeast-derived products, corn meal, bean meal, e.g., soy bean meal, etc. Carbohydrate sources for use in the fermentation media herein can include, for example, sugar, molasses, corn-steep liquor and the like. The fermentation media can also contain a variety of optional ingredients, if desired, such as for example, pH adjustments agents, buffers, trace minerals, antifoam agents, filter aids, etc.

The antibiotic can be prepared by growing the Streptomyces microorganism in an aerated, agitated, submerged culture with the pH of the broth adjusted to about neutral, i.e., from about 6.5 to 7.5. Fermentation can generally be carried out at slightly elevated temperatures, e.g., between about 25° C. and 35° C. Incubation of the broth can be carried out for a period of several days, e.g., from about 4 to 6 days or longer if it is economically advantageous to do so.

As was mentioned previously, the polyether antibiotics forming the zinc complexes utilized in the present invention are glycolic monovalent monoglycoside polyether antibiotics such as etheromycin. The antibiotic etheromycin (also known as C20-12 and CP-38295) has the chemical structure: ##STR1## This structure was set forth in Mitani et al., J. Antibiotics 31, 750-755 (1978) who also noted that etheromycin is the same as the T-40517 antibiotic. According to Westley, Ad. Appl. Microbiology 22, 177-223 (1977), etheromycin is produced from the Streptomyces hygroscopicus microorganism, a culture of which is deposited under number ATCC 31050 at the American Type Culture Collection, 12301 Parklawn Drive, Rockville, Md. U.S.A. Additional details concerning the etheromycin antibiotic can be found in the previously mentioned U.S. Pat. No. 4,129,578 to Celmer et al.

While the above description of the known polyether antibiotic etheromycin identified the antibiotic as being a single compound, it should be recognized that the glycolic polyether antibiotics may be produced as an antibiotic complex of structurally related factors containing varying proportions of each factor. It should therefore be realized that the present invention comprehends the use of the zinc complexes of the various factors of the glycolic polyether antibiotics whether in combination with other factors or in their isolated form in promoting growth enhancing feeding efficiency and treating coccidial infections in poultry, and in stimulating cardiovascular function in animals. Furthermore, zinc complexes of derivatives and isomers of the glycolic polyether antibiotics are also within the scope of the present invention. Therefore, as used herein, the specific name of the polyether antibiotic, e.g. etheromycin, encompasses all of the factors of the antibiotic, as well as isomers and derivatives thereof. It is also within the scope of the present invention that the zinc complexes of the glycolic polyether antibiotics can be used in conjunction with other active ingredients which are also useful for challenging coccidial infections in poultry and/or for promoting growth and enhancing feed efficiency in poultry. For example, the zinc complexes of glycolic polyether antibiotics may have an enhanced effect when used in combination with metichlorpindol. Compositions containing certain designated polyether antibiotics and a pleuromutilin derivative which are useful in treating poultry coccidiosis are disclosed in U.S. Pat. No. 4,148,890 to Czok et al.

To the extent necessary, the above-mentioned patents and literature articles mentioned in describing the known glycolic polyether antibiotics are incorporated herein by reference.

In accordance with the present invention, the glycolic polyether antibiotic, generally in the form of its alkali metal, alkaline earth metal or ammonium salt, is treated in situ in the fermentation broth or beer by adding to the antibiotic containing broth a water-soluble zinc salt. Addition of such a water-soluble zinc salt promotes the formation of a zinc complex of the glycolic polyether antibiotic. Such a zinc complex of the antibiotic, along with zinc complexes formed with residual nitrogen-containing compounds in the broth such as amino acids, polypeptides, and proteins, are insoluble in the fermentation broth liquid. The zinc ions from the added zinc salt apparently form coordination bonds with the oxygen atoms of the insoluble zinc antibiotic complex. On the basis of the formation constants with ligands such as citric acid, lactic acid, and tartaric acid, zinc ions form stronger bonds with oxygen-containing compounds than do ions such as Mg⁺, Ca⁺⁺, Ba⁺⁺, Na⁺, and K⁺.

The zinc salt added to the fermentation broth can be various water-soluble salts which ionize in the fermentation broth. Such salts include, for example, zinc chloride, zinc sulfate, zinc acetate, zinc benzoate, zinc citrate, zinc lactate, etc. Water-soluble zinc salts are generally those which can be dissolved to the extent of about 1 percent by weight or more in water at 20° C. For maximum production of the desired zinc complexes, water-soluble zinc salt should be added to the fermented broth in an amount which is sufficient to fill substantially all of the possible zinc coordination sites of the proteins, polypeptides, amino acids and related compounds, in addition to substantially all of the available coordination sites of the glycolic polyether antibiotic present. This is necessary because in general, nitrogen atoms in the polypeptides, amino acids, etc., form stronger coordination bonds with zinc ions than do the oxygen atoms in the non-glycolic polyether antibiotic. Generally, therefore, zinc salt is added to the fermentation broth in an amount sufficient to provide a zinc content of from about 3 to 12 percent and preferably from about 5 to 10 percent by weight of the dried precipitate recovered from the fermentation broth as hereinafter more fully described.

The amount of soluble zinc salt to be added will depend on the amount of nutrients added to the fermentation broth during the course of the fermentation. An actual amount of soluble zinc salt to be added to broth obtained from a given mash bill can be determined by simple laboratory precipitations followed by zinc analyses on the dried precipitates. When, for example, the preferred zinc chloride salt is employed to form the desired zinc antibiotic complex, advantageously from about 4 to 10 gallons of a 67 weight percent zinc chloride solution (sp. gr. 1.883), can be added to 1000 gallons of fermentation broth.

To form the zinc antibiotic complex in the fermentation broth, pH of the broth is advantageously adjusted to about 6.5 to 7.5 and preferably to about 6.8 to 7.2 after addition of the soluble zinc salt to the fermentation broth.

The insoluble zinc complexes formed upon addition of zinc salt can be readily separated from the fermentation broth or beer by conventional filtration or centrifugation techniques. In this manner, a wet biomass, containing the zinc antibiotic complex, is realized. This wet biomass is resistant to wild fermentations because of its relatively high zinc content. The wet biomass so obtained is easily dried by spray drying or drum drying procedures, and this zinc antibiotic complex-containing dried product can then be used as a feed additive per se. If the antibiotic content of the fermentation beer is lower than desired after completion of the fermentation, crude antibiotic in its sodium salt form can be added to the fermentation beer prior to the addition of the soluble zinc salt. In this manner, the antibiotic content of the biomass composition to be separated from the broth can be increased.

Recovery of the zinc antibiotic complexes of the present invention in the manner described herein provides several important advantages over known antibiotic preparation and recovery processes. The present process, for example, provides a means for recovering relatively high yields of antibiotic in a salable feed additive product. Further, the use of expensive extraction solvents and the cost associated with the process losses of such solvents are avoided. The present process also permits recovery of salable feed values present in the mycelium of the Streptomyces microorganism used to produce the antibiotic. The present process further reduces the cost of waste disposal operations needed in previous processes to deal with the mycelial mat produced during fermentation. Use of this mat as part of the feed additive product, in fact, reduces the cost of the carrier for the antibiotic material being marketed.

The zinc antibiotic complex as hereinbefore described can be added to conventional poultry feed compositions as a coccidiostatic and growth-promoting agent. Such feed compositions generally contain whole or ground cereal or cereal byproducts as an essential nutrient. The feed compositions can also contain such optional additional materials as animal byproducts, e.g., bone meal, fish meal, etc., carbohydrates, vitamins, minerals, and the like. The zinc antibiotic complexes of the present invention are generally employed in the feed compositions to the extent of from about 50 grams per ton to 200 grams per ton, preferably from about 75 grams per to to 125 grams per ton. A feed additive containing a zinc antibiotic complex of the invention can be used in making the feed composition. The additive preferably contains at least about 5 percent by weight of the zinc antibiotic complex, advantageously from about 10 percent to 50 percent by weight of the zinc antibiotic complex.

As was mentioned previously, the zinc complexes of glycolic polyether antibiotics may also be utilized for the stimulation of cardiovascular functions and particularly in the treatment of ailments such as cardiogenic shock, septic shock and congestive heart failure. Preferably, the zinc complexes are utilized for these purposes in a purified form and are administered either orally or parenterally to a patient requiring treatment. Oral administration is particularly preferred for long term treatment of chronic diseases such as congestive heart failure while parenteral administration is preferred for emergency treatment such as in the treatment of shock and of acute heart failure.

Purification of the zinc complexes so that the complexes are more suitable for administration to humans can be accomplished in a variety of manners. A presently preferred method for purification of the zinc complexes from the recovered feed grade zinc complex includes the steps of, after treatment of the fermentation beer with a soluble zinc salt, acidifying the water slurry of the zinc complex with strong mineral acid such as sulfuric acid to produce a relatively low pH, e.g. a pH below about 4, preferably about 2 to about 3, and then extracting the acid form of the glycolic polyether antibiotic from the slurry into a substantially water-insoluble organic solvent such as butyl acetate.

Thereafter, a lower aliphatic alcohol such as methanol is added to the organic solvent containing the glycolic polyether antibiotic. The volume of alcohol added is generally less than or about equal to the volume of organic solvent, preferably about 0.25 to about 1.0 volumes alcohol to about 1.0 volume of organic solvent. A soluble zinc salt such as zinc chloride in the same lower aliphatic alcohol is then slowly added with vigorous agitation to the organic solvent-alcohol mixture containing the polyether antibiotic so as to form the zinc complex of the glycolic polyether antibiotic. Preferably, about 0.5 to 1.0 volumes of the alcohol containing the zinc salt are added per volume of mixture. The amount of zinc salt added should be sufficient to convert essentially all of the contained antibiotic to its zinc complexed form. The formed zinc complexes are then filtered from the mixture, thoroughly washed, and dried.

If greater purification of the zinc complex is desired, the above procedure can be modified to include further purification steps. One such modification is, prior to the addition of the lower aliphatic alcohol, adding an aqueous solution containing an alkali metal hydroxide such as potassium or sodium hydroxide to the organic solvent containing the antibiotic so that the antibiotic is extracted into the aqueous solution. The antibiotic is then re-extracted into the same organic solvent or a different water-insoluble organic solvent such as methyl tertiary-butyl ether after acidification. These steps of the modified procedure can be repeated as many times as desired until the proper degree of purification is achieved. Thereafter, the antibiotic is contacted with the lower aliphatic alcohol and the previously mentioned procedure continued so as to yield the purified zinc complex of the glycolic polyether antibiotic.

In the above description of the purification procedure and modification thereof, the amount of each of the media, i.e., the organic solvent, aliphatic alcohol, aqueous solution, etc., relative to the other media when conducting the procedure may vary considerably, the primary considerations being that sufficient media be utilized to obtain a satisfactory yield of the zinc complex balanced against the cost of the media and the capacity of the available equipment. Generally, the amount of a particular medium used to treat another medium in any of the steps of the above procedure is about 0.1 to 10 volumes, preferably about 0.5 to about 5 volumes, for each volume treated.

Certain advantages are realized by the above procedure where the purified zinc complexes are recovered from the feed grade complexes as opposed to recovery of the purified complexes from virgin mycelia. Among others, the feed grade complexes are filtered relatively easily from the fermentation beer whereas filtering of virgin mycelia is very slow and thus time-consuming. In addition, the feed grade complexes tend to be more concentrated and thus less organic solvent is required in conducting the purification procedure and volume loss of solvent will be reduced.

The zinc complexes of the present invention may be formulated with conventional inert pharmaceutical adjuvant or carrier materials into dosage forms which are suitable for oral or parenteral administration to stimulate cardiovascular function. Such dosage forms include tablets, suspensions, solutions, hard or soft capsules, dragees and the like. The selection of suitable materials which may be used in formulating the active zinc complexes into oral and parenteral dosage forms will be apparent to persons skilled in the art. Such materials, either inorganic or organic in nature, should be of pharmaceutically acceptable quality, free from deleterious impurities and may include, for example, water, dimethylsulfoxide, gelatin albumin, lactose, starch, magnesium stearate, preservatives, stabilizers, wetting agents, emulsifying agents, salts for altering osmotic pressure, buffers, etc. which can be incorporated, if desired, into such formulations.

The quantity of zinc complex which may be present in any of the above described dosage forms generally varies from 10 to 100 mg. per unit dosage. The dosage administered to a particular patient is variable, depending upon the clinician's judgment using the criteria of the condition and size of the patient, the potency of the zinc complex and the patient's particular response thereto. An effective dosage amount of the zinc complex can therefore only be determined by the clinician utilizing his best judgment on the patient's behalf. Generally, parenteral doses should be from about 20 mg. to about 50 mg. for the average size person. Smaller persons or larger persons may require adjustments due to body size. Oral doses, usually capsules, but tablets can be used, generally contain about twice the parenteral dose. The frequency of the administration of the zinc complex depends generally upon the patient's condition and the desired response from the patient. Chronically ill patients may require administration every 2 to 3 hours or once a day, depending on the severity of the disease and the patient's particular response to treatment. Emergency patients generally require only one dose of the zinc complex, particularly those patients in shock.

When administered to a patient requiring treatment, the zinc complexes of the present invention generally have a positive inotropic effect with little or no chronotropic effects and display minimal, if any, adrenergic action, have a rapid onset of action, require a small effective dose, are non-toxic at the effective doses, have a satisfactory duration of action, display a return to the original pre-drug values of cardiovascular activity, and exhibit continued generally identical responses to subsequently repeated identical dosages.

Illustrated in the following examples are preparation and recovery methods for the zinc complexes of glycolic polyether antibiotics as well as feed and feed additive compositions including these zinc complexes and their usefulness as coccidiostats and growth-promoting agents for poultry and in addition, pharmaceutical compositions including these zinc complexes and their usefulness in stimulating cardiovascular function. These examples are in no way to be considered limiting of the present invention to compositions, ingredients, and processes involving the particular zinc antibiotic complex.

EXAMPLE I

A. Fermentation

About 9.5 liters of fermentation beer containing the etheromycin antibiotic is prepared in accordance with the procedure set forth in Example I of U.S. Pat. No. 4,129,578 to Celmer et al. The beer contains at least about 50 mg of the antibiotic per liter.

B. Recovery

To about 2000 ml of fermentation beer about 12.5 ml of a zinc chloride solution (0.24 g Zn per ml) are slowly added with agitation to the fermented beer. The pH is adjusted to a value in the range 7.0-7.4. After the treated beer has been agitated for about 30 minutes, it is filtered, without filter aid, on a Buckner funnel using No. 1 Whatman filter paper. The filtration proceeds rapidly to give a firm cake which is dried in an oven. The final dried product contains a significant amount of the zinc complex of etheromycin.

EXAMPLE II

Objective

To determine the efficacy of the zinc etheromycin complex as an anticoccidial compound for poultry, zinc etheromycin is administered to chickens which are challenged by Eimeria tenella.

    ______________________________________                                                                      Total  24 birds/                                  Test Animals:                                                                            Species: Avian     Number:                                                                               treatment                                  Initial     Hubbard White         Initial                                      Age: 14 days Breed:                                                                        Mountain    Sex: Male Weight: 330 g                                ______________________________________                                    

Test Materials

Zinc etheromycin--32.7% pure by weight

Test Procedure

1. At 14 days of age chicks are weighed and assigned to groups. Immediately after groups are formed (composed of 12 chicks each) chicks are started on their respective medicated feed ration. Each treatment group is replicated twice for a total of 24 birds per group.

2. Seventy-two hours after the initiation of medication, birds are orally inoculated with approximately 100,000 Eimeria tenella oocysts suspended in a 1 cc dose.

3. Control consist of an infected non-medicated group and a non-infected group.

4. Criteria for evaluation are

a. Morbidity (4th-6th day)

b. Mortality (4th-7th day)

c. Incidence of bloody droppings (4th-6th day)

d. Body weight gain

e. Feed per gain

f. Postmortem lesions.

Treatment Groups

    ______________________________________                                         Pen           Treatment                                                        ______________________________________                                         4,  9         Zinc etheromycin,  75 g/ton                                      1,  6         Zinc etheromycin, 113 g/ton                                      5,  7         Zinc etheromycin, 150 g/ton                                      3,  8         Non-inoculated control                                           2, 10         Inoculated control                                               ______________________________________                                    

Rations

Rations employed in the Example II testing are summarized in Table 1.

                  TABLE 1                                                          ______________________________________                                         Chick Starter (Corn)                                                           ______________________________________                                         % Protein    23.0      % Calcium     .98                                       M.E. Kilocalories/lb                                                                        1376*     % Total phosphorus                                                                           .89                                       Ground yellow corn    55.0                                                     Soybean meal 44%      29.0                                                     Fish solubles         2.0                                                      Meat and bone         5.0                                                      Dehydrated alfalfa meal                                                                              1.2                                                      Dried whey            1.0                                                      Animal tallow         4.0                                                      Dicalcium phosphate   1.0                                                      Hubbard super-13      0.8                                                      Vitamin and trace mineral premix                                                                     0.5                                                      Salt                  0.5                                                                            100.5                                                    ______________________________________                                          *M.E.--Metabolizable Energy                                              

Test Results

The results of the administration indicate that a satisfactory challenge is obtained with E. tenella and that all three levels of zinc etheromycin demonstrate activity against this organism. In addition, the birds receiving the two lower levels of zinc etheromycin also show superiority over the controls in weight gain and in feed efficiency.

EXAMPLE III

An experiment is conducted to confirm the indication in Example II that zinc etheromycin has growth promoting properties for chickens.

Objective

To determine the efficacy of zinc etheromycin for promoting the growth and improving feed efficiency in broiler chicks.

    ______________________________________                                                                    Total    60 birds/                                  Test Animals:                                                                           Species: Avian    Number:  treatment                                           Initial                    Hubbard White                                       Age:     2 days   Breed:   Mountain                                                              Initial                                                      Sex:     Male     Weight: 43 g                                        Duration                                                                       of Test: 13 days                                                               ______________________________________                                    

Two-day old broiler type chicks are placed into Petersime starter batteries and given feed and water ad libitum for the duration of the test. Chicks are divided into four treatment groups which are replicated six times with ten chicks (males) in each replication. The test period is 13 days. Pen live body weights are taken at 2, 7 and 14 days of age. Pen feed efficiency measurements are taken at 14 days of age.

Rations

Rations employed in the testing are summarized in Table 2.

                  TABLE 2                                                          ______________________________________                                         Chick Starter (Rye)                                                            ______________________________________                                         Protein       23.2    % Calcium      0.98                                      M.E. kilocalories/lb                                                                         1260*   % Total phosphorus                                                                            0.89                                      Ground Rye            55.0                                                     Soybean meal 44%      29.0                                                     Fish solubles         2.0                                                      Meat and bone meal    5.0                                                      Dehydrated alfala meal                                                                               1.2                                                      Dried Whey            1.0                                                      Animal tallow         4.0                                                      Dicalcium phosphate   1.0                                                      Hubbard Super-13 mineral                                                                             0.8                                                      Vitamin and trace mineral premix                                                                     0.5                                                      Salt                  0.5                                                                            100 lbs                                                  ______________________________________                                          *M.E.--Metabolizable Energy                                              

Test Results

The results of Example III show that, at levels of 50 and 100 grams per ton, zinc etheromycin improves growth response and feed efficiency of young broiler chicks.

EXAMPLE IV

The zinc complex of etheromycin is purified by a purification process, incorporated into a pharmaceutical composition, and is then administered to dogs to stimulate their cardiovascular function.

Purification:

To a liter of fermentation beer slurry containing zinc etheromycin which was produced in a manner as set forth in Example I, sufficient concentrated sulfuric acid is added to acidify the slurry of fermentation beer to a pH of about 3.0. The slurry is then mixed with about one liter of a butyl acetate organic solvent so that the zinc etheromycin is extracted in the solvent. The organic solvent which contains the etheromycin antibiotic is then separated from the acidic aqueous beer and is mixed with about one liter of an aqueous solution of sodium hydroxide having a pH of about 9.0 so that the etheromycin antibiotic will be extracted into the aqueous alkaline solution. Upon separation of the aqueous alkaline solution from the organic solvent, about one liter of methyl tertiary butyl acetate solvent is added to the aqueous solution to reextract the etheromycin antibiotic into the solvent. Thereafter, about 0.5 liter of methanol is first added to the solvent and then about 0.5 liter of a solution of zinc chloride in methanol is slowly added with vigorous agitation. A zinc complex of etheromycin is thereby formed in the methanol-solvent mixture which is subsequently filtered from the mixture, thoroughly washed with additional methanol and then dried. The formed zinc complex of etheromycin is suitable for administration to stimulate cardiovascular function.

Pharmaceutical Preparation:

A pharmaceutical composition containing the zinc complex of etheromycin is prepared, the composition being suitable for parenteral administration.

The following ingredients are utilized to prepare a 5 ml. parenteral solution;

    ______________________________________                                         zinc complex of etheromycin                                                                            50 mg.                                                 propylene glycol        2.5 ml.                                                benzyl alcohol          0.075 ml.                                              ethyl alcohol           0.5 ml.                                                water                   bal                                                    ______________________________________                                    

Treatment:

The above parenteral composition, or any other form of the zinc complexes of the present invention, is administered to animals, e.g. mammals such as, for instance, dogs, prophylactically for, or having, a cardiovascular malfunction to stimulate their respective cardiovascular functions. The procedure utilized is similar to that set forth in U.S. Pat. No. 4,058,620 to Westley. The electrophysical and hemodynamic responses of the dogs are measured before and at various time intervals after intravenous injections of the composition. The parameters measured are myocardial force of contraction, heart rate and blood pressure. Positive inotropic effects are sought with minimal chronotropic effects being manifested in the treated animal.

EXAMPLE V

A zinc complex of etheromycin as purified by the procedure of Example IV is formulated into pharmaceutical tablets suitable for oral administration in stimulating cardiovascular function.

Each tablet has the following composition:

    ______________________________________                                         zinc complex of etheromycin                                                                            25 mg.                                                 lactose                 113.5 mg.                                              corn starch             55.5 mg.                                               pregelatinized corn starch                                                                             8 mg.                                                  calcium stearate        3 mg.                                                  ______________________________________                                    

The tablets are made by thoroughly mixing the zinc complex, lactose, corn starch and pregelatinized corn starch, passing the mixture through a comminuting machine and then moistening the mixture with water in a mixer to produce a paste. The formed paste is screened to form granules and then dried. Calcium stearate is mixed with the dried granules and the granules compressed into tablets using a conventional tableting machine.

While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the spirit and scope of the invention. 

What is claimed is:
 1. A method for producing a zinc complex of etheromycin said method comprising:(a) fermenting a fermentation broth inoculated with a Streptomyces hygroscopicus microorganism capable of producing etheromycin by fermentation of the broth for a period of time and under suitable fermentation conditions in order to produce said antibiotic in said fermentation broth; and (b) providing in said etheromycin containing fermentation broth a water-soluble zinc salt in an amount sufficient to form a zinc complex of etheromycin, which complex is insoluble in the fermentation broth.
 2. A method in accordance with claim 1 further including the step of recovering said insoluble zinc complex from said fermentation broth.
 3. A method in accordance with claim 1 wherein the fermentation of the inoculated broth is conducted at a temperature of from about 25° C. to 35° C. and at a pH of from about 6.5 to 7.5.
 4. A method in accordance with claim 2 or 3 wherein the zinc salt is added to the fermentation broth and is selected from zinc chloride and zinc sulfate.
 5. A method in accordance with claim 4 wherein the pH of the fermentation broth is adjusted to within the range of from about 6.5 to 7.5 after said zinc salt is provided in said fermentation broth.
 6. A method in accordance with claim 2 wherein the insoluble zinc antibiotic complex is recovered from said fermentation broth as part of a biomass which additionally contains insoluble zinc complexes of residual nitrogen-containing compounds present in the fermentation broth.
 7. A method in accordance with claim 6 wherein water soluble zinc salt is added to the fermentation broth in an amount sufficient to provide a zinc content of from about 3 to 12 percent by weight on a dry basis in the biomass recovered from said fermentation broth.
 8. A method in accordance with claim 1 further including the steps of:(c) acidifying the fermentation broth containing the insoluble zinc complex to form the acidic form of etheromycin; (d) extracting the etheromycin from the broth into a water-insoluble organic solvent; (e) adding a lower aliphatic alcohol to the organic solvent containing the etheromycin, the alcohol containing a soluble zinc salt in an amount sufficient to form a zinc complex of etheromycin; and (f) recovering the formed zinc complex of etheromycin from the organic solvent-alcohol mixture.
 9. A method in accordance with claim 8 wherein the aliphatic alcohol is methanol.
 10. A method in accordance with claims 8 or 9 wherein the organic solvent is butyl acetate.
 11. A method in accordance with claim 8 wherein the fermentation broth is acidified to a pH of 4.0 or less.
 12. A method in accordance with claim 8 wherein the zinc salt used in step (e) is zinc chloride.
 13. A method in accordance with claim 8 further including the step of adding an aliphatic alcohol to the organic solvent containing the antibiotic prior to step (e).
 14. A method in accordance with claim 8 further including the steps of extracting the etheromycin from the organic solvent into an aqueous alkaline solution and then extracting the etheromycin from the aqueous alkaline solution into a second water-insoluble organic solvent.
 15. A method in accordance with claim 14 wherein the aqueous alkaline solution contains a metal hydroxide selected from the group consisting of sodium hydroxide and potassium hydroxide.
 16. A method in accordance with claim 14 wherein the second water-insoluble organic solvent is selected from the group consisting of butyl acetate and methyl tertiary butyl ether.
 17. A method for producing a zinc complex of etheromycin which comprises complexing etheromycin zinc or zinc precursor under zinc-etheromycin complexing conditions to produce a zinc complex of etheromycin, the zinc-etheromycin complexing conditions including a fermentation broth in which etheromycin is produced.
 18. The method of claim 17 wherein the zinc or zinc precursor is water-soluble zinc salt. 